I. Field of Invention
The present invention is directed to a heating, ventilation, and air-conditioning system and more particularly relates to a method and system for controlling the stage of a compressor motor and/or fan motor of a heating, ventilation, and air-conditioning system. Preferably, the motor for at least one of the components is a reversible motor that reverses when the power connections to the run winding and start winding are switched.
II. Description of the Related Art
Conventional single phase alternating current induction motors for driving compressors are connected to a source of power by a line contactor. Electric motors typically include a stator which is wound with a start winding and run winding connected to the source of power. The stator winding surrounds the motor which rotates a shaft to produce the motor output. In circuit with the run winding and the start winding are a run capacitor and a start capacitor, respectively. In capacitor start motors, start circuits are connected in parallel with a run winding of each speed of the multi-speed motor. The start circuits include a start winding which is connected in series with start capacitors. During a motor start, both the run winding and the start winding are connected across the motor's power source to magnetically excite the rotor and cause rotation. The start winding and start capacitor combination is used to provide the high torque required during typical start conditions. However, the capacitance necessary to start the motor is typically too large for optimum motor efficiency during normal operation. Therefore, a switch or start relay is usually connected in series with a start capacitor and is used to disengage the start circuit when the motor has reached a predetermined speed or after a predetermined time has elapsed.
When the normally closed start relay deenergizes, the start relay contacts close. If the start relay contacts should happen to open when the run capacitor is fully charged, there is a large amount of energy stored in the run capacitor that can be discharged into the start capacitor when the start relay contactor is closed. There is sufficient power to weld the start relay contacts and thus disable the relay for the next operation.
In view of the foregoing, traditional compression motors are connected to a source of power by a line contactor. Furthermore, traditional compressor motors include a start winding, a run winding, a start capacitor, and a run capacitor. Moreover, certain heating, ventilation, and air conditioning systems include a conventional compressor motor, as described above, and a fan motor and a capacitor for the fan motor. Consequently, compressor motors and the associated components for heating, ventilation, and air conditioning systems may operate in higher power environments and may require higher cost.